Spark plug electrode and method of making same



Augo 1949. c. J. DUSSEAU 2,478,167

SPARK PLUG ELECTRODE AND METHOD OF MAKING SAME Filed Feb. 20, 1943 INVENTOR. (.JDL/55EAU ORNEYS' Patented Aug. 2, 1949 TAT ES PATENT OFFICE SPARK PLUG ELECTRODE AND METHOD OF MAKING SAME This invention relates to sparkplugs, and more particularly to electrodes of spark plugs andto the methods of making the same.

-In theprior art spark plug electrodes of the ring types havingone or moreprongsto cooperate with a-center-electrodeto form the firing-gap, have been made from'stampings of sheet material hat have been relatively inefficient for long continued use-in heavy duty internal combustion engines, for example, airplane engines, because the thickness of the individual-prongs at the firinggapwas too thin to give the-necessary gaplife required to aviation type spark plugs. The thicknessof theprongs was materially reduced-as compared With the original thickness of the sheet material from which the electrode was stamped due to the attenuationof the material during the forming process to obtain the desired contour of the prongs. Therelatively thin sections of the prongs reduce to a certainextentthe-capacity for r rial by sparking. This acceleration in material erosi'on-tendedto shorten the useful life of the spark plug and made it necessary to overhaul the airplane enginesafter-a shorter period-cf operation.

The present invention provides a multi-prong electrode fora spar-k plug which obviates these difficulties by giving the prongs of the electrode substantially the same thickness-as I the thickness of the originalsheet from which the electrode is fabricated. This desirable result is brought about by a series a of steps in the forming operation in which the outside-diameter of the ring of the electrodeis originally stamped to a dimension material-1y larger than the finaloutside dimension. The electrode itself is then compressed from the larger outside diameter-to the smaller outside diameter oi'the final electrodein a "constricti'ng press so that thejuxtaposition of the upwardly turned pron'gs is changed to a closer-relationwhereby morematerial is available for the formation of the prongs arising from the'large size "of the" original outsidediameter of T the electrode. This method of forming the electrode has the advantage of avoiding the attenuationoi the material which previously esulted inarelatively thin section or thickness in thetprongs of the completed electrode.

The fact that the original step in the'formation of the electrodewhen the blank is first struck from the'sheet material is {made witha larger outside diameter 'allows the use of dies and punches having greater strength and durability; During the manufacturing process the punches and dies used in the fabrication of electrodes are given a longer life expectancy so that the cost of fabricating these electrodes is materially reduced.

face suitable fora particular firing condition in the enginecylinders.

"It is a further objector this invention 'to provide a'method'o'f making multi-prong sparkplug electrodeswherein'the stock used for forming the prongs'is obtainedfrom material within the perimeter of'the' electrode and thereafter collapsing the. perimeter whereby the thickness of the prong a'djacentthe spark gap is approximately the same thickness as thesheet stockfrom which the electrode is fabricated.

Itis a further object of this invention-to provide a machine 'suitable for making multi-prong sparkiplug electrodes, which collapses the supporting web of the electrode from a relatively large diameter to'the predetermined diameter of the'compl-eted electrode. 7

Other objects and advantages of this invention relating to the arrangement, operation and function of the related elements of the structure, to various details of constructionyto combinations of parts and to-economiespf manufacturawill be apparent to those skilled in the art upon considerationof the following description and appended claims, reference being had to the accompanying drawings forming'a part of this specification wherein'like reference characters design'ate" corresponding parts inthe several views.

"Figil is a perspectiveview of'i'sheet stock. showing the various steps "during ithe'early forming operationszofthe electrode.

Fig.2 1538. plan view,-partly in'section, of a die usedin one step of forming theelectrode. and is taken alongthe line 2-2 of Fig. i 3.

-Figs3 is-a sectional elevation of the die, taken along the line. 3-13 of Fig.2.

.Eig. 41's. aperspective view of the electrode,

showing .the shaving operation.

'Fig. .5 .is a sectional elevation, showing the relation of'ithe prongs .ofithe electrode.

Fig. 6 is an elevational view, partly in section, of the spark plug to which the electrode has been applied.

Fig. 7 is a sectional elevation of a modification of the electrode form.

Referring to the drawings, particularly to Fig. 6, a spark plug is shown having a shell iil pro-- vided with a threaded portion H by which the spark plug is adapted to be screwed into the cylinder block of an engine. A ceramic insulator I2 is provided which encloses a central electrode l3, whose lower end It projects from the bottom of the insulator l2 and cooperates with electrode l which is conveniently brazed or otherwise attached to the lower end of the threaded portion ll of the shell in a recess H5. The prongs ll of the electrode l5 cooperate with the tip M of the central electrode to form the spark gap of the spark plug. The details of construction of the spark plug of this type are well known in the art and need not be described in further detail. This invention relates particularly to the ground electrode l5 and to the methods of making the same.

Referring now to Fig. 1, a strip of sheet material I 8 is provided whose width is slightly larger than the external diameter of the blanked form IQ of the electrode, this width being necessary in order to facilitate the blanking operations in a punch press (not shown). The thickness of the strip sheet stock I8 is selected with a view of obtaining sufllcient thickness to give necessary strength to the connecting web 20 of the electrode, which is of the ring type having preferably three inwardly projecting prongs 2| which are shown in an early step of the fabrication of the electrode in Fig. 1. The thickness of the sheet stock I8 is one of the factors which predetermines the thickness of the prongs and if a greater amount of material is desired in the prongs to provide more material available for gap erosion, a thicker sheet may be selected.

The first step in the forming operations of the electrode comprises piercing a triangular-shaped aperture 22 which provides faces 22a which at a later period become the end faces of the prongs 2|. The next step in the forming operations is another piercing step wherein three bights 23 are struck from the material which communicate with the aperture 22 to form a cloverleaf-shaped aperture as shown in Fig. 1. The next step in the forming operations comprises bending of the prongs 24 which project inwardly in the second step of the operation to form the cloverleaf aperture to the condition shown in the left-hand position of Fig. 1 wherein the prongs 24 have been bent substantially to normal use position or angularly to the plane of the sheet material l8. Immediately after the bending of the prongs, and preferably a part of the same step, the electrode I9 is blanked from the sheet as is clearly shown. This leaves a circular aperture 25 in the sheet stock l8 as is clearly shown. The blanked electrode I9 is shown immediately below the aperture 25.

The diameter of the aperture 25, and the outside diameter of the blanked electrode I9, is such that the web 2|] is given a ring formation to support theupwardly bent, inwardly disposed prongs 2| so that the length of prong desired, may be obtained from the amount of material available in the strip sheet l8 while the unbent prongs are still in the plane of the sheet stock as shown at 24. The prongs, as shown at 2|, are substantially the same thickness as that of the sheet I8 and are bent upwardly as shown without attenuating the material in the prongs to any great extent.

These four steps of piercing, forming and blanking are preferably performed by a multiple die having three stages, the first of which pierces the aperture 22 to form the end faces of prongs 24, the second step which is also a piercing operation forming the prongs 24 by striking the cloverleaf aperture; and the third stage performing the upward bending of the prongs 2| and the blanking operation of the web 20. These four steps are illustrated with reference to the piece of sheet material 58 Fig. 1. With the sheet material 8 in the form of a long strip, a continuous operation may be performed by advancing the strip from right to left as shown in Fig. 1, leaving scrap material in the form of a strip |8 pierced by a series of apertures 25.

As has already been discussed, the outside diameter of the blanked electrode I9 is considerably larger than the outside diameter of the completed electrode l5 as mounted in the plug shown in 6. The ranked electrode by reason of its larger outside diameter, disposes the upwardly-bent prongs 2| in a relation having considerable space between the prongs inasmuch as the inside surfaces of the prongs 2| fall in the surface of a cylinder considerably larger than the diameter of the tip l4 of the center electrode and would give too wide a gap if the blanked electrode were to be mounted in a plug. This invention provides a method whereby web 20 of the blanked electrode l9 may be collapsed uniformly along radial lines so that the outside diameter of the electrode is decreased to substantially the outside diameter of the completed electrode. The diameter of the collapsed electrode is still allowed to remain slightly larger than the finished electrode in order that a shaving operation, illustrated in Fig. 4, may be performed to provide the electrode with the exact outside diameter desired.

The dies necessary to perform the operations of piercing, forming and blanking are well known in the art and need not be described in further detail.

In order to perform the collapsing operation wherein the web 20 is collapsed to a smaller diameter, a novel form of die is provided as is generally shown in Fig. 2. In this figure a plan view of the die is shown just after collapsing operation of the blanked electrode has been completed. The die is provided with three reciprocating bars 26 positioned in an angular relation apart and are adapted to reciprocate in this angular relation toward a common center. Each sliding bar 26 is provided with a square aperture 21 through which projects a square cam stem 28 in substantially normal relation thereto. These stems 28 are shown in transverse section in Fig. 2 and in longitudinal section in Fig. 3, only one being shown in the latter figure.

Referring to Fig. 3, a cam section 29 is provided on the stem 28 at substantially a mid point thereof so that when the stem 28 is retracted toward the left (as shown by the arrow) it will be clear that the action between the cam section 29 and the aperture 21 will cause a retreat of the bar 26 in an outwardly direction from the common center of action of the three slide bars. The slide bars 26 are provided with guides 30 cooperating with each side of the bar to maintain the linear movement converging toward the common center.

In order to move the stem 28 in and out of the apertures 2'! of the slide bars 26, a head 3| is provided which preferably is attached to a punch Tne'terward' faces 6f the-siide bars zs are' given a wdge:shape'rormatim-'2swans terminate an ai'c port-ion flli tifihitiif has-thesameradiiis' as the outside diameter 6f i the eltrode *Web after the christriet'ing bperation is I completed. The are ZBbj-rm the ioi wai'd iace of'the sl-ide barififextends for i",-=measi1red froin'the commen center of actionso that the "ees'lidebars ZSXbyac'ih cavermg 120* of are, l'form a complete circle cirewn sciibi-ng the *peiiine'ter of the "constricted electrode. In-order that' the'sli'de bars fii -irn'at'y have amplestrfith toapply' the necessary force to aeooriiblish the donstrieti'rig operation on the eletrode, they are made"1'elatively' thiek and the forward faces are chamfered at Z'BCsothat the most advanced portion is adjacent thelewer side of the' slide-bar 2*6 where-the slidebar fi (:ooperates with' 'an anvil -The anvil 3 5 tieoperates with orie I side of the *web of the electrede While the slide bars' 2 cooperate with the-'perimetrieal edge thereof. shined-aperture ais provided in -t-heantil throhgh-Whilra h'revable memb er' 35 is adapted A to reciproeat longitiidin-ally ina line parallel to the reeiioroa'ting' e;etionof thecam bars fii. The movable meniher flfiis of *sp'l-in'ed formation toprvefitrttutidh in aperture r'm and is provided with" at head a'i' -afijacerit its lower-end whichcoperateswitwa tra sversel reciprocating bar 38 by a cam format-M11 39 c'ohfornied' a's-a I fljflged'griiovygrihpirig head fi. "As the bar 38 i is reci reeetem in direct-ion bf the arrow showm '3,'tnr ou gn sandal i'ianip'u1ati0nbf a l'ver ifl 3 the inovz jhie' 'fnemberfifi is thrust to the ri ght'mr d WhWaifdl-y inthe aperture 35a of the anvil 39, forming a stripping action on the eleetrecle. The smiles its-conveniently ernbedded in a'hase i' as shown tt'ith'the aperture 35a exteriding 'through both. 'The base *4 I is provided with-"afiilot" fin whieh the rec'iprocating'barlfl moves lever iii mdves therec'iproeating bar as bvmeans of 91x1 finesse-arrangement 43; the lever being adapteu t meve "about a pivot 44 as Shed-VII in phantom in 'Fi'g. 2.

lihe ubperend (lft h'arid erid"Fig- 3) of the movable member 36 is "contdured in a manner to give"the eleetrodeits'finaI firm; having reference to thesha 'zie 6fthe prorigs -i 1 and the conformatio'nef-the c1over-leafepening' 2-3 in the electrede. For this purpose a central spindle-Eris=iirovided on the nibvahie 'ixn'eiiibe'r 36 flanked by "bosses 1 46 which fit iri-to' ol'ove'rl'e af shafa ed openings 23 of the leetfode. The'eritral spihdle'fi of the movable member G'coop'e'rates with an aperture 4'1 of a mbvabl d1 attafih'e' to the head 3 Poi the punch press and afda'pted to' be roi ii-ocated-therby at thesame tirri thiait theeem bars 2a are bihg'reoipfo'atd. The aperture 41 "is ferably positioned in the m'niber 48*Whiliis conveniently triean ttith the c lieflportien fl. "shareware, er lower, fade 50' of the die pert-tennis rarmect'as a truncated cone SO as to fit be'twe'en' the chamfld forward taees 26c of:the' sl'ide bars 26 with th I; f ace 50a 'o0perating with= the f ace of =th'e elec trdde w'liose eppesiteraee rests on -t1ie'anvi1 '35 and the'inovable meifi-ber iafi, the electrode being formed by 1 relative longitudinal inoven'i'eht between the diefiortibn mil-1d the'anvil=35. The electrode is also beingformed-substantiallysimultan'eo'usly by the 1atera1==moveinerit ofthe" three slide bars 25 irioving in toward a comifion 'center under the'aetionmfthe cam bars 28.

A cycle of operation of this'machine preferably ;,Ho1l6ws the seqiieneeie'given"hereinafter: 'In the openin phase'th'e tieadfil of thel pun-h firess is retracted to the le'ftg'inthe-directionof the arrow shown in Fig; 3, to a point Where theportion of the cam bars='28be'ybnd the 'caim sectioniil oo'pr -erate with the apertures?! in the slide bars i'fi. Inasmuch as th-e cam sections 2 9 are displaced outwardly; the slide bars 2 6, "'lindereentrol 'of tlie portions of the cam'bar's'w pos'i'tionedbeyond the cam "sections 29, will'be disposed in'a ia'o'sitibn' most remote from the 'com-"mon center of action. This position of the slide bars 26 is-show'ninphan tomin Fig. 2 which showsthe 'sl'ide bars in their most outward position. -The armsurfaees 1% are sufficiently sebarated so-th'at the blanked 'e1ec- :11;- tiode l9, as shown in Fig/L'Which'is to-be co1- lapsed inwardly toa smailer outsidediameter; is readily placed between the arvsfirface andnpon the anvil '37 and the forward faee-"ofthe reei-pro catizig member--35. -Irrasmucifasthediameter of 3:: "the central spindle 45 is somewhat smaller With reference to the juxtapdsition of therprongs 2 l' of the blanked electrode t9, ahdthe bosses lfi -are sofriewhat' 's'mal'ler tharith'e 'cloverleaf openingsof the blanked electrode; no difiiculty "will beexperi 4= -enr'ae d branoperatorfinpositioning the blanked elctrode ms'ion the 'end of the movablemem'oen-fi-Q to its i estingpl'acewn the anvil. =The m-anual lever controlling" the: position-of the movable member 36 is substantiallyin the positionshown in solid linesin Fig. z' with the reci irocating bar 32 in "substantially-the p'osi-tion shown in -Fig. 3, that is with the'he'ad 3l pos'itioned at a ii'oifit-near the highest portion of the cam siirfaee 39.

With-the fia'rts in this po'siti'o'nf-the constricting operation on "the electrode- "may begin. The operator piaeesthe blank'ed- 'electrode was shown in Fig. 1, in-t'o' positibn 0n the end 'of the movable member 35 so tha-t' the 'c'entral s' iindl'e &5 is plaeedhetweenthe pron'gs2l with" the bbsses cooperating with the" clovrl'a'f openingsbetween thehrongs" and theweb zfl. The pur'ieh press is then started in oriefation which-advances *the headiil toth ght; as shown -inFigfi, so-as to bring the cam seetion z i1\to'= opei'able relation with theafie'itiire 21 in the' 'slid'b'ars 26*Which simultaneously advanees all three slide b ars-in- Wardly to the i oint where" they coritaizt 'tl're he web- '2H -oftheblanked eleetrode. also attached= to'the hea'd 3 of the"pi "eh 'fires's, advaxi'ces toward the center spindle is ormemevatie member 36. Whemth'e calm "seetien 29 has fiassed' substantially 1 through thea'pefture 21"6f"t1'1'e'Slide-bars .lfi tvhich are moved inwardlytherebytne outside diameter of z the Web 2!] of the blahked eleetrodewiscollapsed ifiwafdly and "deie'ased to tl'iefliametr 6f a 'il 'c'le formed-hy the afc' filth. positioned'tm the forward faleesoFthe thr e simmers-2s, There'after "the di'e" friiiilierlt fnfitesqhto-h 75 cavity-"formed between tlie Sli'de'ba'rs Z s tb -tlii iist the electrode against the anvil 35 within the curved faces 26b of the three slide bars 26. This action irons the face of the electrode and, through the action of the knockout pin 49, the ends of the prongs are ironed at the same time. The stroke of the head 3| is adjusted so that the space between the movable bars 26 is such that the blanked electrode positioned therein is conformed to the desired dimensions with small openings being provided between the slide 'bars 26 to allow excess material to flow outwardly. This is clearly shown in Fig. 4 where small nibs 60, formed on the perimeter of the web 200., are shown, this being excess material.

Upon completion of the forward stroke of the head 3i, the direction of movement thereof is reversed to the left as shown in Fig. 3, which causes a retreat outwardly of the slide bars 25 and of the die member 48. At this point force is applied to a rod 6|, movable in an aperture 62 in the head 3|, to advance the knockout pin 39 with reference to the die 48. The action of the knockout pin 49 releases the electrode from the forward end of the die member 48 so as the head 3| retreats the electrode will remain in position upon the forward end of the movable member 36. The movable member 36 is then retracted downwardly by manual reciprocation of the bar 38 to strip the constricted electrode from the forward face of the movable member 36 so that an operator may reach into the cavity of the die to remove the constricted electrode member. The operator then places another blanked electrode member [9 in position in the die cavity and a new cycle of operation begins.

The outer dimension of the constricted electrode member is made slightly larger than the desired outside diameter of the completed electrode. A shaving operation is then performed with dies that are well known in the art to remove the surplus material, as is shown in Fig. 4. The electrode 29a has the desired outside diameter and a ring 2022 has been shaved from its perimeter as is well understood in the art and need not be described in greater detail.

The completed electrode is then positioned in the shell Ill of the spark plug, as shown in Fig. 6, by brazing, or welding, or the like.

In Fig. 7 a modification of the completed electrode is shown in which the thickness of the material at the base of a prong 65 has been substantially reduced in thickness by bumping at 66 so that the stiffness of the prong is substantially reduced to facilitate bending of the prong 65 with relation to the tip M of a center wire (Fig. 6). The form of the electrode shown in Fig. provides the prongs of the electrode with the same diameter throughout its length with the base of the prong being displaced a slight angle, for example 7, with reference to the plane of the connecting web. In many cases this type (Fig. 5) electrode has the disadvantage that adjustment of the prongs by bending so as to vary the spark gap between the prong and the tip of the center wire is made very diflicult due to the inherent stiffness of the prong. Furthermore, the fact that the angular displacement between the prong and the plane of the supporting web is small, there is little tolerance to allow for any substantial gap adjustment by bending.

In Fig. 7 the angle between the prong and the plane of the supporting web has been increased to 30 which gives a substantial tolerance to allow displacement of the prong inwardly by bending to allow for spark-gap adjustment. The base 66 of the prong is also reduced in thickness by bumping which decreases the stiffness of the prong and allows more ready adjustment of the prong during change of spark gap length. The bumping operation, which decreases the cross section at 66 of the completed electrode as shown in Fig. 7, is preferably carried out by changing the conformation of the forward face of the movable member 36 so that the prong is conformed through the inter-action of the die member 48, the anvil 35 and the movable member 36. In other respects the same steps are followed forming this type ofelectrode as have already been described with reference to electrode shown in Fig. 5.

It is to be understood that the above detailed description of the present invention is intended to disclose an embodiment thereof to those skilled in the art, but that the invention is not to be construed as limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of being practiced and carried out in Various ways without departing from the spirit of the invention. The language used in the specification relating to the operation and function of the elements of the invention is employed for purposes of description and not of limitation, and itis not intended to limit the scope of the following claims beyond the requirements of the prior art.

What is claimed:

1. The method of forming a multi prong ground electrode of the ring type suitable for use with spark plugs, comprising, piercing, blanking and forming the electrode from sheet material in a series of steps, maintaining the diameter of the ring supporting the inwardly disposed prongs substantially larger than the dimension of the ring in the completed electrode, collapsing the ring in a radial direction to reduce the diameter of the ring to substantially the diameter of the completed electrode, and thereafter attenuating a portion of the prongs adjacent the ring to reduce the section thereof.

2. The method offorming multi-prong ground electrodes of the ring type suitable for use with spark plugs, comprising, piercing an aperture in sheet stock, the sides of the aperture forming end faces of the several prongs, piercing a series of bights in communication with the aperture to form inwardly projecting prongs, forming the inwardly projecting prongs to an angle substantially normal to the plane of the sheet stock, blanking a ring from the sheet stock supporting the inwardly projecting prongs, said ring having a diameter substantially larger than the diameter of the completed electrode, collapsing the ring in a radial direction to change the juxtaposed relation of the inwardly projecting prongs to decrease the diameter of the ring to substantially the diameter of the completed electrode and thereafter attenuating a portion of the prongs adjacent the supporting ring to reduce the section thereof.

3. The method of formin multi-prong ground electrodes of the ring type suitable for use with spark plugs, comprising, piercing an aperture in sheet stock, the sides of the aperture forming end faces of the several prongs, piercing a series of bights in communication with the aperture to form inwardly projecting prongs, forming the inwardly projectin prongs to an an le substantially normal to the plane of the sheet stock,

blanking a ring from the sheet stock supporting the inwardly projecting prongs, said rin having a diameter substantially larger than the diameter of the completed electrode, collapsing the ring in a radial direction to change the juxtaposed relation of the inwardly projecting prongs to decrease the diameter of the ring to substantially the diameter of the completed electrode, attenuating a portion of the prongs adjacent the supporting ring to reduce the section thereof, and thereafter shaving the outer edge of the electrode to the exact dimension of the final electrode.

4. The method of forming multi-prong metallic ground electrodes for spark plugs comprising piercing, blanking, and forming the electrode from sheet stock with a ring forming a connecting web between the inwardly and downwardly projecting prongs, a portion of said downwardly projecting portions of said prongs forming sparking surfaces, said ring having a diameter substantially larger than the diameter of the completed electrode, placing the sparking surfaces of the prongs in predetermined relative relation with each other by collapsing the web inwardly, and substantially simultaneously ironing the metal of the prong at and adjacent the sparking surfaces.

5. The method of forming a multi-prong metallic ground electrode for spark plugs comprising piercing, blanking, and forming the electrode 1 10 ironing the metal of the prongs at least at the sparking surfaces.

6. The method of forming multi-prong metallic ground electrodes of the ring typesuitable for with spark plugs comprising, piercing an aperture in sheet stock, piercing a series of bights in communication with the aperture to form inwardly projecting prongs, forming a portion of the inwardly projecting prongs to an angle substantially normal to the plane of the sheet stock to comprise sparking surfaces, blanking a ring from the sheet stock supporting the inwardly and downwardly projecting prongs, said ring having a diameter substantially larger than the diameter of the completed electrode, placin the sparking surfaces of the prongs in predetermined relative relation with each other by collapsing the web inwardly, substantially simultaneously ironing the metal of the prongs at least at the sparking surfaces, and thereafter further decreasing the diameter of the ring by shaving while maintaining the predetermined relations of the sparking surfaces.

CORNELUIS J. DUSSEAU.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,284,263 Duffy Nov. 12, 1918 1,350,568 Rydbeck Aug. 24, 1920 2,102,493 Thode Dec. 14, 1937 2,135,240 Paulson Nov. 1, 1938 2,180,528 Kasarjian Nov. 21, 1939 2,309,613 Horton Jan. 26, 1943 2,356,102 Tognola Aug. 15, 1944 2,356,104 Tognola Aug. 15, 1944 

